It is well known in the prior art to utilize an optical grating to provide positional feedback information to an optical scanning system as the light beam utilized by that scanning system traces across a page from which information is to be extracted or upon which information is to be recorded. It is desirable, in such systems, to know exactly where the first grate begins in order to synchronize the position of the scanning beam with a page and the information being read from the page or to synchronize the scanning beam upon the page where the information is being recorded.
Most prior art devices have utilized a second detector to assure that the optical scanning system knows precisely when the scanning beam has terminated its scan to thereby accurately identify when and where the next scan has begun.
A typical optical facsimile system utilizing a beam to scan a document and a grating to identify the location of the scanning beam is shown in U.S. Pat. No. 3,849,592 which issued Nov. 19, 1974 entitled "Graphic Data Redundancy Reduction For Text and Half-Tone Optical Facsimile System" by Bernard M. Rosenheck which is assigned to the same assignee as the present invention.